macbook pro monitor

SITUATION: I have a 2015 15" Macbook Pro. I've been trying to get an external monitor, but the two i bought(and returned) had horrible text resolution - very fuzzy. They were Samsung curved 32" and 27" monitors, HD, CF series. I was thinking the size was too large for scaling, so got the smaller, but same fuzzy text. It's intolerable, hard on the eyes. I tried all the suggested fixes I saw online, even had Samsung take remote control of the situation, and they could not find anything.

QUESTION: Is this text fuzziness because with a MacBook Pro (Retina display) do you need to get a 4K, UHD external monitor? Is there some special compatibility that I am not aware of? Does anyone have experience with fuzzy text on the MacBookPro using a standard HD monitor, and what does one do about it?